Seeing that it is so popular, I decided to do it myself, in my own way.
I'd say it's one of the most delicious dessert bread I've ever eaten!
I leave the recipe below
Recipe
Dough for bread with cocoa
150 g sourdough starter
300 ml of water (room temperature)
50 g of sugar
500 g of flour for bread
30 g of cocoa
10 g of salt
chocolate chips - 100 g

Dough for decoration (if desired)
50 g sourdough starter
250 ml of milk
1 egg
50 g of sugar
450 g of flour
1 teaspoon of salt
60 ml of melted butter

Method of preparation
First, feed the starter, 50g of sourdough starter + 50ml of water + 50g of flour, cover and leave for at least 4 hours at room temperature. For the second starter, take 30 starters + 30ml of milk + 30g of flour + 1 teaspoon of sugar.
After the sourdough starter has been activated, has air bubbles, and has tripled in volume, it is ready to be used in the dough. take 150 g of starter, add water and sugar, mix well. Mix the flour with the cocoa and pour it on top, add salt and knead until it becomes a homogeneous dough (5-7 minutes). The dough will be a little sticky, homogeneous. Cover with a towel and leave at room temperature. In the meantime, prepare the second dough.
Put the sweet starter, milk and sugar in a bowl, mix well, then add flour and salt, knead a soft dough. Add the melted butter, knead until the butter is incorporated. You will get a very soft dough, don't panic, cover the bowl with a plastic bag, and put the dough in the refrigerator until the next day, without handling it.
After an hour, it's time to stretch and fold the dough with cocoa. And do the same after 2 hours. Then let the dough rise for 2-3 hours, until you notice that it is fluffy and has increased in volume.
After the dough has risen, form a loaf, adding the chocolate chips to it, put it in the basket, or the banneton you have, and put the bread in the refrigerator for the whole night.
The next day, preheat the oven together with the cast iron or clay cauldron (which you have) to 250 C
Take the sweet dough out of the fridge and roll it out with a rolling pin, then cut circle shapes (I used a glass and nozzles). Then take the loaf out of the fridge, take it out of the basket and put the sweet dough on top. Fix it and put it in the hot cauldron, put the lid on and put it in the oven for 40-45 minutes (I cook with the lid on until the end) at 250 C